In the related art, an image forming apparatus such as a scanner, a copying machine, or a multi-function peripheral (MFP) includes an image sensor to read an image of a document (document image) using an illumination device and a lens array in which plural lenses are arranged. In addition, in the image forming apparatus such as a printer, a copying machine, or a multi-function peripheral (MFP), by using an light emitting element such as an LED and a lens array, light rays emitted from the LED are imaged on a photoconductor drum through the lens array, and the image is formed (exposed) on the photoconductor drum. The lens array is formed, for example, by combining plural lenses and apertures.
However, in such a lens array, when the optical axes between lenses through which one light ray passes deviate from each other, imaging characteristics deteriorate and non-uniformity in light intensity can become severe. In addition, when plural lenses and other optical path elements such as apertures are combined, misalignments among the elements during assembly causes deterioration in imaging and printing performance.
JP-A-2002-62407 discloses an imaging element array in which imaging elements are combined to avoid deterioration in performance caused by misalignment during assembly. However, since there are two reflective surfaces in the disclosed device at a position where a light flux width is wide, surface accuracy has an effect on image formation. Therefore, there is a problem in that it is necessary to increase the time needed to mold the lens assembly so that a desired surface accuracy can be achieved.